Under normal circumstances, the most up-to-date version of Windows begins to drag in a majority of market share (defined as the percentage of PCs that run it) in the year of its release. Windows 10 1809 has not enjoyed this level of success so far. In fact, according to a new report by AdDuplex, it has only attained 6.6% of the total market share from 2016 to 2018.
https://www.notebookcheck.net/Windows-10-1803-has-retained-nearly-84-of-the-OS-market-share-in-2018.388201.0.html